This proposal aims to characterize speech changes in patients who lose hearing as a result of bilateral acoustic neuromas (Neurofibromatosis 2). We will monitor patients who have already lost hearing in one ear from this disorder, and are at risk of losing hearing in the other ear. Because rapid hearing loss in the functioning ear will occur in some of these patients, their speech can be studied before and after deafening, providing a unique opportunity to detect subtle and progressive changes to speech parameters following deafening. While gross speech impairments do not commonly result from loss of hearing in adulthood, there are numerous subtle changes. The careful study of the speech parameters that do and do not deteriorate, and of the different time courses that deteriorating speech parameters follow, should illuminate the role of audition in underlying control mechanisms in speech. With a carefully selected population of patients, referred to us from the Neurogenetics Unit of N.I.N.D.S., Epidemiology Branch, and the Neurofibromatosis Clinic at the Massachusetts General Hospital, we will initially make acoustic and physiological recordings of speech production and test speech perception to establish baseline values. Those values will be used to assess changes in speech parameters in a subset of these patients whose hearing in the functioning ear begins to decline rapidly. On this subset of patients, we will perform repeated assessments including perceptual testing and acoustic and physiological recordings of their speech. We will seek to relate the measures of deteriorating perceptual function to the profile of degeneration of speech parameters. This work will be guided by experimental hypotheses concerning: timing of changes in speech parameter values and reliance on auditory feedback; relations among changing speech parameters; and relations between perception and production. To explore these hypotheses, we will measure within subjects, longitudinally: 1) acoustic characteristics of the production of speech segments (temporal and spectral variables) and prosody (fundamental frequency, intensity and temporal variables); 2) underlying physiological variables (parameters of laryngeal function, respiration and airflow, and coordination of oral, nasal and laryngeal articulations); and 3) speech reception (tests of phoneme, word, and sentence perception). The in-depth acoustic and physiologic analysis of the speech in combination with measures of the perception of this highly unusual group of subjects, from whom we can uniquely record pre-deafening measures of speech production, should provide otherwise unobtainable information on the role of auditory feedback in the control of speech production. From a clinical perspective, the results should also be useful in helping to understand and manage the communication problems encountered by these patients.